Duplicate strings in array while using 'dom-repeat' throws error: 'Uncaught Error: unexpected key undefined'

[ajtejankar]

Following is the element I made which throws an error mentioned in the title.

<link rel="import" href="../polymer/polymer.html" />

<dom-module id="data-list">
    <template>
        <template is="dom-repeat" items={{data}}>
            <div>{{item}}</div>
        </template>
    </template>
    <script>
        Polymer({
            is: 'data-list',

            properties: {
                data: {
                    type: Array,
                    value: function() {
                        return ['Random', 'Random'];
                    },
                    notify: true
                }
            },

            attached: function() {
                this.splice('data', 0, 1);
                this.splice('data', 0, 1);
            }
        });
    </script>
</dom-module>

This is caused by storing values of an array as keys in the object pmap.

[fredefox]

I have noticed this too. Only after seeing this issue did I realize that it happens when you use non-unique values in the array. Do you have a work-around?

[ajtejankar]

@fredefox Using objects instead of primitive values should do the trick.

[fredefox]

Right you are! Thank you.

[ajtejankar]

I would really love to contribute a PR for this bug if somebody guides me on how to go about it. It would be my first ever PR on GitHub :).

[MeTaNoV]

Just go ahead by following this: https://github.com/Polymer/project/blob/master/Contributing.md

[StokeMasterJack]

I too am getting this error. I am using an array of object which may contain duplicates. It happens on this line:

this.splice('selected', indexToRemove, 1);

and it seems t happen when deleting a duplicate for the second time.

[Pupix]

/sub

[electrovir]

I have an issue related to this but I am not getting an error thrown. Instead, when I use dom-repeat to bind an array with non-unique strings to input boxes, editing the text inside any input besides the first (using normal user interaction) changes the value in the first input box.

Also, this will happens even if the initial values of the bound array are not identical, but become identical later by user input.

[TimvdLippe]

This has been fixed in Polymer 2: http://jsbin.com/fuqarizedo/edit?html,console,output